It is a trend to make electronic products small in size and compact in thickness. There are many issues, such as heat dissipation, which need to be settled during the design process. One of these issues is how to consolidate necessary components into an integrated circuit (IC) or a printed circuit board (PCB). An electronic component can be embedded in a printed circuit board during the printed circuit board manufacturing processes. The technique started from buried resistor technology Ohmega Technologies, Inc. Although it was only passive components can be used in the beginning, it becomes well accepted to the industrial now days that active components can be applied by various modifications and invention.
Among all integrated circuits, there are several kinds which have specified functions and need to work interactively with external environment. Exemplary examples are charge-coupled devices (CCD) and complementary metal-oxide-semiconductors (CMOS). A fingerprint reader sensor and a mouse sensor are typical products for the CCD and CMOS, respectively. The fingerprint reader sensor needs to detect change of capacitance and the mouse sensor needs to receive light change over a surface. Even those integrated circuits are embedded into a PCB, it is required a proper arrangement and configuration for the integrated circuits to expose to the external environment. Meanwhile, a good design for the integrated circuits to work is important, as well.
Reviewing the prior arts, there are several inventions that have focused on some of the requirements mentioned above. First, the U.S. Pat. No. 8,083,954 discloses a method for fabricating a component-embedded printed circuit board. The method includes: providing a carrier plate having a plating metal layer plated thereon, disposing an electronic component on the plating metal layer of the carrier plate, laminating a metal layer onto the plating metal layer having the electronic component disposed thereon and the carrier plate by a dielectric film, removing the carrier plate and exposing the plating metal layer, and patterning at least one of the metal layer and the plating metal layer to be a circuit layer. '954 focuses on how to reduce the overall thickness of a printed circuit board. It can not apply to active components for embedding processes.
Next, the U.S. Pat. No. 8,302,299 discloses a method of manufacturing a multilayer printed circuit board of a built-in electronic device. It provides a substrate having a copper clad laminate and a first dielectric layer. The first dielectric layer is laminated onto the copper clad laminate and has a cavity for accommodating the electronic device. A second dielectric layer is laminated onto the substrate and electronic device to produce a base circuit board with an embedded electronic device. A build-up circuit layer is formed on the base circuit board. The first and second dielectric layers are made of a plastic material. Obviously, the embedded electronic device can not be the CCD or CMOS because there is no window for a portion to expose to the external environment.
Last, the US Patent Application No. 20130092420 depicts an invention which relates to a method of manufacturing an embedded printed circuit board. An embedded multilayer printed circuit board includes first, second and third circuit substrates, and a flexible circuit substrate. The first circuit substrate includes a first base layer and a first electrically conductive layer. The second circuit substrate includes a second base layer and a second circuit layer. The second circuit substrate also defines a receiving hole. The third circuit substrate includes a third circuit layer, a third base layer, a fourth circuit layer, and an electronic element mounted on the third circuit layer. The third circuit layer and the fourth circuit layer are formed on the opposite sides of the third base layer. The electronic element is received in the receiving hole. The flexible circuit substrate includes a flexible base layer and a flexible circuit layer. The first circuit layer is electrically connected to the fourth circuit layer by the flexible circuit layer. The invention indicates a simple and low-cost method to manufacture embedded printed circuit boards. However, it is still fail to expose the embedded electronic element. As well, no solution for protective an expose embedded active component is mentioned.
Therefore, a method for manufacturing printed circuit board which has an electronic component embedded, allowing the electronic component exposed to external environment, providing necessary designs for the electronic component to work and minimizing the overall thickness of the printed circuit board assembly is still desired.